Acetabular labral tears are an increasingly recognized source of hip pain in young adults, especially females, and have been linked to the premature development of hip osteoarthritis (OA). Recently, femoroacetabular impingement (FAI) has been implicated as a cause of labral injury and OA. In FAI, hip pain occurs in the presence of a structural abnormality of the acetabulum or femur which results in early contact between the bones during hip flexion and internal rotation. Current treatment for FAI includes surgical procedures to resect or reorient the femur or acetabulum or both. While structure does contribute to hip pain, increasing evidence suggests that movement patterns may also play an important role. The long-term goal of this line of research is to improve treatment for hip pain, especially in young adults, which will prevent or slow the progression of chondral damage and thereby reduce the need for hip arthroplasty. The purpose of this project is to assess the movement patterns of people with FAI compared to people without hip pain and to test for sex- and limb- specific differences in these patterns. Identification of differences in movement patterns which may contribute to hip pain can improve non-invasive treatment for people with hip pain. To test for these differences, we will assess movement patterns using kinematic data collected during movements including walking, stepping down, supine straight leg raise and prone hip extension on subjects with FAI and subjects without hip pain. We hypothesize that subjects with FAI will display movement patterns which are closer to their end-range hip motion than subjects without hip pain. We believe that these movement patterns contribute to a subject's hip pain. We also hypothesize that females with FAI will display different movement patterns than males with FAI. We anticipate this sex difference in movement patterns because there is an unequal distribution of the structural abnormalities among females and males, and because a sex effect has been noted in other lower extremity injuries (e.g. ACL tears, patellofemoral pain). Furthermore, as subjects often have unilateral pain despite bilateral structural abnormalities, we hypothesize that subjects with FAI will display different movement patterns of the painful hip than the unimpaired hip. The knowledge gained from this research has the potential to redirect treatment for people with FAI by identifying sex-specific movement patterns which could be targeted by inexpensive and non-invasive therapeutic interventions. It also could be used to develop prevention programs focused on neuromuscular retraining.